#include <bits/stdc++.h>
using namespace std;
#define debug(v) cerr<<#v" = "<<(v)<<"\n";
#define debugvec(v) do{cerr<<#v<<" = [";for(int i=0;i<v.size();i++)cerr<<v[i]<<(i==v.size()-1?"":", ");cerr<<"]\n";}while(0);
#define debugvecp(v) do{cerr<<#v<<" = [";for(int i=0;i<v.size();i++)cerr<<"[ "<<v[i].fst<<" "<<v[i].snd<<" ]"<<(i==v.size()-1?"":", ");cerr<<"]\n";}while(0);
#define fst first
#define snd second
#define gcd(x,y) __gcd(x,y)
#define OnlineJudge(s) freopen((s".in"),"r",stdin); freopen((s".out"),"w",stdout);
#define fastIO() cin.tie(0)->sync_with_stdio(0);cin.exceptions(cin.failbit);
#define boolsolve() cout<<(solve()?"Yes":"No");
using ll=unsigned long long;
using ull=unsigned long long;
using pll=pair<ll,ll>;
using vll=vector<ll>;
using vpll=vector<pll>;
using vvll=vector<vll>;
const ll INF=1e18;
const ll MOD=1e9;
const ll MAXN=1e6;
void solve(){
ll n, d, m;
cin >> n >> d >> m;
vpll A(m);
for(int i=0; i<m; i++){
cin >> A[i].fst;
A[i].snd=i+1;
}
sort(A.begin(),A.end());
auto ok=[&](ll k){
queue<ll> q; ll z=0;
for(int i=1; i<=n; i++){
while(z<m && A[z].fst==i) q.push(A[z++].fst);
if(!q.empty()){
if(i-q.front()>d) return false;
for(int j=0; j<k && !q.empty(); j++) q.pop();
}
}
return q.empty();
};
ll l=0, r=INF;
while(l<r){
ll k=(l+r)/2;
if(ok(k)) r=k;
else l=k+1;
}
cout << l << "\n";
queue<ll> q; ll z=0;
for(int i=1; i<=n; i++){
while(z<m && A[z].fst==i) q.push(A[z++].snd);
for(int j=0; j<l && !q.empty(); j++){
cout << q.front() << " ";
q.pop();
}
cout << "0\n";
}
}
int main(){
fastIO();
//OnlineJudge("")
ll t=1;
//cin >> t;
while(t--){
solve();
//cout << "\n";
}
return 0;
}
